Beta Librae
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Beta Librae (β Lib / β Librae) is the brightest star in the constellation Libra. It also has the traditional name Zuben Eschamali (pronounced zoo-ben-es-sha-mali) and the Latin name Lanx Australis. The name Zuben Eschamali is derived from an Arabic phrase Al Zuban al Shamaliyyah meaning "the northern claw".[1]
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[edit] Description
Beta Librae is a blue dwarf star of spectral type B8 (main sequence star), a little less evolved than Sirius. It has apparent magnitude 2.7.
At a distance of 160 light years from Earth, it is about 130 times more luminous than the Sun and has a surface temperature of 12,000 kelvins, double that of the Sun. This high temperature produces light with a simple spectrum, making it ideal for examining the interstellar gas and dust between us and the star. Like many stars of its kind, it is spinning rapidly, over 100 times faster than the Sun. This type of hydrogen-fusing star often appears blue-white, but Beta Librae is often described as greenish, the only greenish star visible to the naked eye.[2]
The small periodic variations in the magnitude of the Beta Librae imply the presence of a companion star which is not directly observable from earth.[3]
Data from the Hipparcos catalogue:[4]
- Bayer name for the star: Beta Librae
- Proper name of the star: Zubeneschamali
- Right Ascension in hours and minutes for epoch 2000: 15h 17m
- Declination in degrees for epoch 2000: −9°22'57"
- Galactic longitude of the star: 352.0
- Galactic latitude of the star: +39.2
- Spectral classification: B8V
- Visual magnitude of the star: 2.61
- Absolute magnitude of the star: -0.84
- The Hipparcos parallax of the star (x1000): 20.38
- The error in the parallax (x1000): 0.87
- The distance in light years (=3.2616/parallax): 160
[edit] History
According to Eratosthenes Beta Librae was observed to be brighter than Antares. Ptolemy, three hundred and fifty years later, said it was as bright as Antares. The discrepancy may be due to Antares becoming brighter, but this is not known for certain. It could simply be caused by Beta Librae being a variable star with a variability of 0.03 of a magnitude.[1]
[edit] References
- ^ a b AAS (2006). LIBRA – A Balanced View. Auckland Astronomical Society. Retrieved on 2006-07-03.
- ^ Jim Kaler (2006). Zubeneschamali. Stars. Retrieved on 2006-07-03.
- ^ Mark Fisher (1999-2006). Zuben Elschemali. The Electronic Sky. Retrieved on 2006-07-03.
- ^ Dan McGuire (1997). The Brightest Stars (.pdf). Retrieved on 2006-07-03.
[edit] External links
- for more examples of Arabic star names (such as Rigel, Fomalhaut, Algol, and Betelgeuse) see
- Moh'd Odeh (1998-2006). Arabic Star Names. Islamic Crescents' Observation Project. Retrieved on 2006-07-03.
